Rotor assembly

ABSTRACT

A rotor assembly for attaching a rotor member to a rotatable shaft including a shaft opening through which is positioned a rotary shaft. A U-shaped retainer is also positioned through the shaft opening between the shaft and the sidewall of the opening with one leg of the U-shaped retainer positioned against a rear surface of the rotor block and the other leg of the retainer positioned within a slot formed in the front face of the rotor block. Within the slot, between the leg of the retainer and the sidewall of the slot is positioned a setscrew which engages threads formed in the sidewall of the slot, the setscrew bears against the base of the retainer forcing it against the shaft thereby locking the rotor into place against the shaft.

United States Patent [72] Inventor John P. Doering, Jr.

Santa Ana, Calif. [211 App]. No. 19,618 [22] Filed Mar. 16, 1970 [45]Patented Aug. 17, 1971 [73] Assignee Beeltmnn Instruments, Inc.

[54] ROTOR ASSEMBLY 7 Claims, 7 Drawing Figs.

[52] US. Cl 287/52.08 [51] Int. Cl F16d 1/06 [50] Field of Search287/52.08,

[56] References Cited UNITED STATES PATENTS 642,275 I] 1900 Zacharias287/5208 UX 2,151,045 3/1939 Ploehn 287/5208 ,1 492 11126. 231/5219?!Assistant Examiner-Andrew V. Kundrat A!torneys-Fem L. Mehlhoff andRobert J. Steinmeyer ABSTRACT: A rotor assembly for attaching a rotormember to a rotatable shaft including a shaft opening through which ispositioned a rotary shaft. A U-shaped retainer is also positionedthrough the shaft opening between the shaft and the sidewall of theopening with one leg of the U-shaped retainer positioned against a rearsurface of the rotor block and the other leg of the retainer positionedwithin a slot formed in the front face of the rotor block. Within theslot, between the leg of the retainer and the sidewall of the slot ispositioned a setscrew which engages threads formed in the sidewall ofthe slot, the setscrew bears against the base of the retainer forcing itagainst the shaft thereby locking the rotor into place against theshaft.

I PATENTED AUG] Han I 3,600,013

FIG. 2 '6 FIG. 4 2 260 3| 32 22' j 22a 22b FIG. 5 7 INVENTOR JOHN F.DOERING JR.

ATTORNEY ROTOR ASSEMBLY BACKGROUND OF THE INVENTION The presentinvention relates to rotors of the type employed in rotarypotentiometers, switches and the like, and is more particularly directedto the structure for affixing the rotor to a rotatable shaft and forpermitting indexing of the rotor at particular angular positions on saidshaft.

Potentiometers and switching devices usually employ a rotor block ormember which is afiixed to a rotatable shaft and which carries aslipring or a conductive wiper adapted to make electrical contact with aresistance element or switch contacts positioned adjacent the rotor. Therotor is preferably formed of a nonconductive material such as brass,Bakelite or other plastic material. Existing rotor mounting arrangementsusually require the drilling or coring of a radial hole for a setscrewand then tapping this hole for the insertion of the setscrew whichengages the shaft and retains the rotor in position with respect to itsangular location on the shaft. Drilling and tapping are expensivemachine operations. If the rotor is formed of aplastic material it isnecessary to provide complicated molds using a core, for forming thehole for the setscrew and means must be provided for removing or slidingthe core from the mold so that the part may be removed.

Another problem with regard to setscrew-type rotors" is the difficultyin assembling or aligning the rotors with respect to the shaft. Once thesetscrew is turned down onto the shaft it produces a small indentationwhich makes it difficult to change the rotor position or phasing" by asmall amount since the setscrew tends to fall back into the indentationwhich has previously been formed in the shaft.

It is, therefore, an object of the present invention to provide animproved rotor structure which may be easily attached to a rotary shaft.

It is another object of the invention to provide a rotor structure whichpermits phasing in very small increments at all positions around theshaft.

It is another object of the invention to provide a rotor structure whichmay be cast or molded in a simple mold which requires no sliding cores.

Further objects and advantages of the invention will become apparent tothose skilled in the art from a reading of the following detaileddescription of the preferred embodiments of the invention, taken inconjunction with the accompanying drawing wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged perspective viewof the rotor block of the invention;

FIG. 2 is a view taken from the external end of the rotor showing theslot and the setscrew mounted therein;

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG.

FIG. 4 is a view of the rear surface of the rotor; and

FIGS. 5, 6 and 7 are perspective view of three different modificationsof the retainer to be employed with the rotor for securing the setscrewand locking the rotor to the shaft.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, thereis shown a rotor block 11 which, in the illustrated embodiment, isrectangular in shape. It will be understood that the outer dimensionalshape of the rotor block is not essential to the invention and it may becylindrical, oblong, or any other shape, such as the rectangular shapeshown. The rotor may be fabricated of a metal, such as aluminum orbrass, or preferably it may be molded out of a plastic, such as aglass-filled nylon material. The rotor block is provided with a frontsurface 12 and a rear surface 13 (see FIG. 4) and includes a shaftopening 14 extending through the block. A drive shaft 16 is positionedthrough the opening 14.

While the rotor is employed for moving electrical contacts, switchingelements, etc., these components are not illustrated because they arenot pertinent to those aspects of the invention associated with mountingthe rotor on the shaft.

As will be seen in FIG. 1, the rotor block 11 is provided with a slot 17which may be machined into a metal rotor or may be formed in a plasticrotor when the rotor is molded. In the illustrated embodiment, the slot17 extends from the outer or external end 18 of the rotor block to theshaft opening and intersects the shaft opening. In this embodiment, theend sections 17a and 17b of the groove are smaller in cross section thanthe central section 17. Section 17b is provided with partial threads 19along the sidewalls of the slot, which are adapted to receive and matewith the threads formed on the setscrew 21 when it is inserted into thesection 17b of the slot. Portion 17 of the slot is made larger than theremaining portions 17a and 17b in order to facilitate insertion of thesetscrew 21 into the lower portion 17b of the slot.

In order to retain the setscrew 21 in place against the threads 19within the slot, and in order to provide a means for locking the rotorto the shaft, there is provided a substantially U-shaped retainer 22which is inserted into the shaft opening 14 between the shaft 16 and thekeyed-space 23 (see FIG. 4) between the shaft and the internal surfaceof the opening 14 of the rotor block. The U-shaped retainer 22 ispreferably formed of metal, such as steel, brass or aluminum, and isprovided with a base 24 and two upstanding legs 26 and 27. The base 24abuts against the outer surface of the shaft 16 with leg 26 positionedagainst the rear face 13 of the rotor. Leg 27 extends upwardly into theslot 17 and retains the setscrew 21 in place within section 17b of theslot and forces the setscrew against the threads 19 formed in the slot.

Obviously, the retainer 22 is inserted into the keyed shaft opening 14prior to insertion of the shaft 16. Once the shaft 16 is positionedwithin the shaft opening 14, the retainer 22 cannot be removedtherefrom. The leg 27 of the U-shaped retainer securely holds thesetscrew 21 in place so that when the setscrew is rotated, it may betightened down against the base 24 of the retainer and imparts a forceon the retainer against the shaft. The retainer base 24 acts as a padfor the setscrew 21 so that it cannot mar or produce indentations in theshaft.

Preferably the legs 26 and 27 of the retainer extend into recessesformed in the front and rear surfaces respectively of the rotor block.In the case of the leg 26, it is positioned in the recess 28 (see FIG.4) formed in the rear surface of the block. The leg 27 extends intoenlarged recess 29 formed over the section l7b.In the illustratedembodiment recess 29 is the same width as the central portion 17 of theslot. The keyed portion 23 of the shaft opening, as well as the recessedportions of the rotor block, are engaged by the sides of the retainerand the retainer legs thereby securely locking the rotor to the shaftwhen the retainer is tightened onto the shaft,

The retainer employed in FIGS. 2 and 3 is shown in perspective in FIG.5. It may be desirable to employ other such retainers having desirableshapes for various purposes. One such shape is that shown in FIG. 6 inwhich the retainer 22a is provided with a rear leg 26 and a curved frontleg 27a, the inner diameter of which is adapted to receive the curvatureof the setscrew. In this arrangement the curvature of the retainersecurely holds the setscrew in place within the slot formed in the rotorblock. In FIG. 7, there is shown still another embodiment of theretainer in which the legs 31 and 32 are vastly different in size.

In order to phase"or position the rotor 11, an appropriate tool, such asa hex key" wrench, is inserted through a hole in the housing of thedevice supporting the shaft. The tool is passed through the end 17a ofthe slot in the rotor and positioned into the hex head of the setscrew21. The setscrew is rotated and backed away from the retainer base 24 torelieve the locking force of the retainer against the shaft 16. Theshaft is then rotated while the rotor is retained in position by thetool. Then the setscrew is again tightened against the retainer to lockthe rotor to the shaft.

Obviously the setscrew may be provided with other means for itsrotation. For example, thesetscrew may be provided with a slotted endwhich may be rotated by means of a screwdriver. It is desirable,however, that the opening 17a of the slot, through which the tool isinserted, be only large enough to clear the tool or wrench. Thus, whenthe wrench or tool is inserted into the head of the setscrew, the sidesof slot 17a aid in holding the rotor 11 securely in a desired alignment.The alignment between the hex head 30 and the opening 17a permit therotor to be precisely positioned while the shaft is rotated.

The rotor of this invention is especially suitable for ganginga numberof rotors onto a single shaft, such as in an arrangement using aplurality of single-turn potentiometers. In such a case it is necessaryto phase or locate each of the rotors with regard to its angularposition on the shaft. By using rotor structure of the presentinvention, a number of rotors may be phased with no special fixturing.After the shaft is inserted through the rotors, their setscrews areinitially clamped down. Then it is a simple task to individually adjustthe position of each rotor by loosening its setscrew 21 and rotating theshaft to its desired position. Then setscrew is tightened against thebase 24 of the rotor retainer and the process repeated for each rotor.

It may be desirable to provide a knurled portion on the shaft to assureimproved frictional cooperation between the shaft and the base 24 of theretainer. While this has not been found actually essential, it may bedesirable in some instances where the rotor is of substantial mass.

While in accordance with the patent statutes there has been describedwhat at present is considered to be the preferred embodiments of theinvention, it will be obvious to those skilled in the art that variouschanges and modifications may be made therein without departing from theinvention and it is. therefore, the aim of the appended claims to coverall such changes and modifications as followed in the true spirit andscope of the invention.

What I claim is:

l. A rotor for a potentiometer or the like comprising:

a rotor block having front and rear faces and a shaft opening extendingtherethrough;

a slot in said front face of said rotor block, said slot communicatingat one end thereof with said shaft opening, said slot having threadsformed in a portion of the sidewall thereof adjacent said shaft opening;

a rotary shaft positioned through said shaft opening in said rotor;

a shaft retainer also positioned within said shaft opening, saidretainer having a substantially U-shape with a base section positionedbetween the shaft and the sidewall of said shaft opening and with oneleg of said U-shaped retainer positioned into said slot in said frontface and the other leg of said U-shaped retainer positioned against saidrear face of said rotor block, the base section of said U- shapedretainer abutting against said shaft in said shaft opening;

a threaded setscrew positioned in said slot between said sidewallsthereof and said one leg of said U-shaped retainer, said leg of saidretainer forcing said setscrew into engagement with said threads in saidsidewall of said slot, said setscrew applying a force against said baseof said retainer when said setscrew is rotated within said slot therebycausing said base to firmly engage the surface of said shaft and locksaid rotor to said shaft.

2. The rotor defined in claim 1 in which said slot on said front faceextends to the end of said rotor body so that said setscrew may beengaged by a tool inserted through said slot from the end of said rotorbody.

3. The rotor defined in clam 2 in which said setscrew includes meansadapting said setscrew for rotation by a tool inserted through saidslot.

4. The rotor defined in claim 1 in which said slot is semicircular incross section and a portion thereof adjacent said shaft opening isprovided with partial threads formed on the bottom portion of the slotwhich en age the threads'of said setscrew.

5. The rotor defined in c aim 4 m which said one leg of said retainer isformed with a curvature adapted to receive he curved portion of saidsetscrew.

6. The rotor defined in claim 1 which a recess is formed on the rearface of said rotor block to receive said leg of said retainer with thesides of said leg of said retainer abutting against the sides of saidrecess thereby retaining said retainer securely in place with respect tosaid block.

7. The rotor defined in claim 1 in which the shaft opening is key-shapedwith the shaft extending through the circular portion of the key-shapedopening and the retainer is positioned in the flatted portion of thekey-shaped opening.

1. A rotor for a potentiometer or the like comprising: a rotor blockhaving front and rear faces and a shaft opening extending therethrough;a slot in said front face of said rotor block, said slot communicatingat one end thereof with said shaft opening, said slot having threadsformed in a portion of the sidewall theReof adjacent said shaft opening;a rotary shaft positioned through said shaft opening in said rotor; ashaft retainer also positioned within said shaft opening, said retainerhaving a substantially U-shape with a base section positioned betweenthe shaft and the sidewall of said shaft opening and with one leg ofsaid U-shaped retainer positioned into said slot in said front face andthe other leg of said Ushaped retainer positioned against said rear faceof said rotor block, the base section of said U-shaped retainer abuttingagainst said shaft in said shaft opening; a threaded setscrew positionedin said slot between said sidewalls thereof and said one leg of saidU-shaped retainer, said leg of said retainer forcing said setscrew intoengagement with said threads in said sidewall of said slot, saidsetscrew applying a force against said base of said retainer when saidsetscrew is rotated within said slot thereby causing said base to firmlyengage the surface of said shaft and lock said rotor to said shaft. 2.The rotor defined in claim 1 in which said slot on said front faceextends to the end of said rotor body so that said setscrew may beengaged by a tool inserted through said slot from the end of said rotorbody.
 3. The rotor defined in clam 2 in which said setscrew includesmeans adapting said setscrew for rotation by a tool inserted throughsaid slot.
 4. The rotor defined in claim 1 in which said slot issemicircular in cross section and a portion thereof adjacent said shaftopening is provided with partial threads formed on the bottom portion ofthe slot which engage the threads of said setscrew.
 5. The rotor definedin claim 4 in which said one leg of said retainer is formed with acurvature adapted to receive he curved portion of said setscrew.
 6. Therotor defined in claim 1 which a recess is formed on the rear face ofsaid rotor block to receive said leg of said retainer with the sides ofsaid leg of said retainer abutting against the sides of said recessthereby retaining said retainer securely in place with respect to saidblock.
 7. The rotor defined in claim 1 in which the shaft opening iskey-shaped with the shaft extending through the circular portion of thekey-shaped opening and the retainer is positioned in the flatted portionof the key-shaped opening.